It should normally be blank. RStudio bundles its own copy of Qt; we've seen some cases where users have set QT_PLUGIN_PATH to point at a separate (incompatible) version of Qt and so this would force Qt in RStudio to attempt to load an incompatible plugin and crash.
Unfortunately that doesn't appear to be the case here so we'll need to try something else. The next thing to try (unfortunately it'll take some extra work) is to prepare a Windows Minidump to see if we can figure out what's happening when RStudio crashes.
You can try creating a Windows Minidump. First, you need to enable Minidumps explicitly. You can try importing the registry file here to enable minidumps:
Restart your computer afterwards to ensure the registry updates take effect.
Next, perform the action that causes the crash to occur. If we're lucky, the crash dump will be written to a folder at:
C:\Users<username>\AppData\Local\CrashDumps
replacing with your Windows username as appropriate. Note that AppData is a hidden folder, so if you're trying to navigate to it in the Windows explorer you'll need to ensure hidden files and directories are made visible.
Then, within the folder, you should find files of the form:
.exe..dmp
Please share the file with us. If the file is large, you might consider uploading it to a cloud storage provider (DropBox, Google Drive, Windows OneDrive) and sharing a link to that file for us to examine.
If you'd like to later disable Windows minidumps, you can run the following registry file: