To simulate a fresh install, you need to delete any accrued application state. To do this, you'll want to delete select folders in your plugin sandbox (location found in the Sandbox Home field in Project structure | SDKs | [your IntelliJ IDEA plugin SDK].
- config folder contains IDE app-level configuration, including app-level libraries, SDKs, recent projects, etc.
- system folder contains indexes and caches, deleting it is similar to File | Invalidate Caches action.
- plugins folder contains plugins that you additionally manually installed to the started IDE. (Likely don't want to delete
Dart.) - test folder will also appear as soon as you run some tests. (Deleting it when tests fail with no visible reason can sometimes help.)
(NOTE: after removing configuration info, you may need to re-prepare the flutter-intellij plugin for deployment in order for it to show up in your fresh runtime workbench: Build > Prepare Plugin Module 'flutter-intellij' For Deployment.)