You can use the Extensions Manager control panel to choose the extensions you want to load at startup.
Open Extensions Manager and choose the base extension set at the top (instead of "My Settings"). That one just loads the basic extensions needed for your system to run.
The downside is that some of your added software may not work without special extensions being loaded. Create a new set in Extensions Manager and tick off the special extensions you also want to load.
This is a very simplistic explanation. You'll need to read up a bit about Extensions Manager to get more detail.
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