bin/console plugin:refresh
# you should get an output like this
[OK] Plugin list refreshed
----------------------- ------------------------------------ ------------- ----------------- -------- ----------- -------- -------------
Plugin Label Version Upgrade version Author Installed Active Upgradeable
----------------------- ------------------------------------ ------------- ----------------- -------- ----------- -------- -------------
SwagBasicExampleTheme Theme SwagBasicExampleTheme plugin 9999999-dev No No No
----------------------- ------------------------------------ ------------- ----------------- -------- ----------- -------- -------------
1 plugins, 0 installed, 0 active , 0 upgradeable