How do I keep IntelliJ from closing my Editor Tabs automatically?
Intellij IdeaEditorIntellij 15Intellij Idea Problem Overview
When opening more than 10 Editor Tabs, IntelliJ automatically closes my least used Tab each time I open a new Tab.
How can I increase this limit?
More recent IntelliJ settings are accessed differently than older versions.
Intellij Idea Solutions
Solution 1 - Intellij Idea
Change the Tab Limit under the Tab Closing Policy settings.
Open your IntelliJ settings: Select File -> Settings -> Editor -> General -> Editor Tabs.
Look for Tab Closing Policy -> Tab Limit and change the value to a higher integer.
You can also select to either close non-modified files first or less frequently used files first once your tab limit has been reached.
Solution 2 - Intellij Idea
For recent versions on Mac, Configure Editor tabs is under 
In the Editor --> General --> Editor Tabs, Under Closing Policy, change the Tab limit as per your requirement
Solution 3 - Intellij Idea
If you need more than 100 tabs:
> By default, the maximum number of open tabs that you can allow is > limited to 100. If you want to increase that limit, press Ctrl+Shift+A > or choose Help | Find Action from the main menu. In the popup that > opens, start typing Registry, select the corresponding item and press > Enter. In the Registry dialog, search for the ide.max.editor.tabs key > and change its value.
Solution 4 - Intellij Idea
Adding an answer to help anyone else with a similar problem. OSX+Catalina on JetBrains/PyCharm was having closing all tabs when I lost focus on the application. When I came back the "Synchronization" action happened (top right circle arrow spins) and all windows are reset (many closed as a result). My fix was to disable in the settings. Appearance & Behavior > System Settings > Disable everything under the "Synchronization" section. You may need to seek out other "sync" options in settings.