Also late to the party (just people lying around with hangovers now!), but as above, ContextKeeper looks like it is a good does everything utility, but I've not tried it as would need to buy/license/etc and with work that's another set of red tape and hoops to jump through. So as @Benjol said, hacky work-around of maintaining hidden .suo files works for my needs...

So, real low effort fix is if you want to save your session/windows, just copy the hidden .suo file as say saved.suo, and then make a batch file called restore-saved-stuff which is just one line of

echo F|xcopy /H /Y saved.suo .suo

If you want clean session, delete the hidden ".suo" file.

Could probably put things onto right-click contexts, params on batch files, and so on, but this is a quick and dirty way to save your session.

For me, the .suo files are in the \.vs\project\v16 folder (v16 = VS2019)