FWIW, just as a check I took one of my own importers and recompiled it using the very latest Visual Studio 2019 (v142). I use Windows SDK version 10.0.
Interestingly, after applying the very latest Visual Studio 2019 upgrades, my code did not directly compile anymore, so I had to add some #includes which were not necessary before…
Anyway, after dropping the recompiled dll into the Importers directory, the importer still operated as expected.
In this particular case I am still using the SDK_WIN_x64_2019-3-253 (I have not upgraded that solution to use SDK_WIN_x64_2020-0-363 yet, I guess it will work, but I do not know with certainty).
I am working within Windows 10 Version 1903.
I am still using the Sketchup version 20.0.373 as the later versions gave me serious problems. These Sketchup problems have been discussed on the forum, they might have been fixed by now, but I have not taken the time to check this.
I have not taken the (latest?) xml_to_skp code, so I do not know how this behave. It is summer vacation now so I am just occasionally within reach of my computer…
I updated to Sketchup 20.1.235 on another machine (I will not change from 20.0.373 on my main machine without some serious testing).
Dropping my own recently recompiled importer to this machine works nicely as well.
Recompiling and linking my own importer with SDK_WIN_x64_2020-0-363 appears to give no problems as well.
Oddity: On Sketchup’s SDK page (https://extensions.sketchup.com/sketchup-sdk) they refer to the latest Windows SDK version as 20.0.362. Well, the minor version I have is 363 (not 362).
Maybe just a typing error on the SDK page?