Thank you for posting this workaround!
It worked for me, and I have a fairly low end machine - an i7 with 16GB memory and a GTX 1060 gpu with 6GB memory. After the last update, my FPS went from around 30 or so to 10-15 in some places, particularly when approaching an airport. My setup was laggy even just on the World menu, and the FPS issues were not related to a single location.
With your workaround, I now run 30-40 FPS in the “worst” areas - a huge improvement!
How do you hide the developer mode bar at the top though? I’m assuming for this work around to continue working, the scenery editor and developer mode have to be open?
I don’t think this entirely corrects my performance drop, but there is certainly a significant difference when using this work around during a large FPS drop. Cheers for the tip!
9:22 Central us time here. I rebooted my computer. I deleted my MSFS Content.xml file, as it was full of stuff I don’t even have in the sim. I restarted MSFS, and went to 76T. No drop in FPS. (holding around 42).
I’m not using the DevMode work-around.
WHY?
Did Asobo make a silent change? Did my deletion of the Content.xml fix this? Dumbfounded!
Ah, okay, I thought you meant you manually resized the window rather than minimising 
this is interesting, where is the content.xml file and what does it hold?
i.e. Do we lose anything if we delete it?
Also if you are using this workaround I have found that once you’re about 10 miles away from the troubled airport you can close the scenery editor so the sims continues as normal. I think.
My Content.xml file shows something like this:
just a list of installed airports etc. I cannot imagine how this file impacts on FPS but you never know…
After deleting this file and restarting MSFS it should automatically be built up again …
Can’t find this on my PC. 
Which one did you delete? A search finds several. Can you provide a path? Are you on Steam or MS Store?
I would like to try it.
Running devmode (especially if you are tinkering with scenery edit) changes the way MSFS2020 loads assets.
That this would have an impact on FPS seems reasonable.
The area in general is quite data dense. There are major airports and a lot of other airfields nearby.
When these load they are also loading all the ground assets. Parked aircraft, vehicles, ground crew as well as the scenery files for those airports themselves. The airfields do not need to be within visual range.
Toggling into DevMode changes some of this behaviour.
I bought the sim through steam and the file is located in:
C(or other main location of your PC)/user/(your user name)\AppData\Roaming\Microsoft Flight Simulator.
But I still have not tried that way.
I am absolutely fine with you disagreeing. 
But “You can’t play the sim!” is hyperbole to an extreme extend, don’t you think? I am flying every day for several hours. Of course I experience the current fps drop bug which can be quite annoying. But still, I think it’s whining, when Asobo clearly acknowledged the bug and is working on fixing it but some people still repeat over and over again how bad everything is.
Of course I have the bug too, what made you think otherwiese?
Yes. The moment you close those windows, fps drops again. At least you can minimize them.
On longer flights it might happen that your target airport does not load correctly and terrain textures are not loaded (the airport textures, the underlying satellite textures are displayed). So this workaround does help mostly when making lokal flights etc.
I went into LocalCahe and renamed content.xml to BU_content.xml. Started MSFS an went to 76T. Still 2 FPS, the usual performance, so no difference there.
I looked at the newly created content.xml and compared it to the original one and the new one had 3 less lines in it. I did not examine to see what changed.
What I did notice was that the game loaded faster and was quicker to get to the taxiway after pressing Fly Now.
Ok so just tried it. It definitely improves the framerate. From 11fps it goes to 60 in the fps counter. HOWEVER, it does not feel 60 at all. It feels more like 30fps even if the counter says 60fps.Weird.
When I close scenery editor, the fps drops back to around 5fps, loads up assets that it most likely hid during the editor (like runway/taxi signs) and then goes back to normal, which is around 50fps for me.
I have no idea why 76T works for me without the DevMode fix. All I did was delete the Content.xml file, which rebuilt. Then started the sim, and no FPS drop. Unless Asobo has snuck in a fix of some sort, I have no idea what changed.
I am glad it is sorted itself out for you 
NOTE: this workaround does mess with scenery loading. KSFO did not load in for me (missing terminal buildings, ground textures not processed meaning they were straight off of bing satellite imagery, cracks on the runway, etc etc) since the scenery editor was open and I’ve heard reports of custom scenery also not loading in correctly. So use this as you will but be aware it messes with scenery loading.
I can also confirm that this method is messing up the loading for sceneries.
you CANNOT do a flight to another area with this workaround.
Objects, Terminal buildings etc… are not loaded currently.
