Hi @Anto BAro ,
Welcome to Microsoft Q&A!
Have you tried to create a new project and check if the (+/-) is working in other projects?
Please update your VS2019 to latest version 16.11.27 and launch your VS2019 in Safe Mode (run devenv /SafeMode in Developer Command Prompt for VS 2019). It will run the VS without any extensions, check if the installed extensions affect or not.
You can try to reset environment settings for Visual Studio 2019.
Sincerely,
Anna
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