The 787-10 in FS2020 has two boarding doors and the 747-8 in FS2020 has 3 boarding doors (two fwd, one in the upper). But in FS2020 you can only have one boarding exit. Two boarding door can have two stair in the fwd doors and can have dual jetway (not in FS2020, but wishing to have it). Three boarding door like the 747-8 can have two stair in the two fwd and one in the upper, three jetway (two in the fwd doors and one in the upper).
This is an example of a A330 being connected with two jetway:
This is an example of a A380 being connected with three jetway:
But there is a problem. In real life in some airport such as for example SVMI, it will only use one stair even when there is more than one boarding door, probably due to limitation, restriction or it just how they operate that way. Here is an example of a 757-200 of SBA Airlines in SVMI with only one stair: