As Oracle has documented, there is an SQL History folder and it is larger (has more SQL queries that return in about a year) than the SQL History toolbar (a couple of months).
Here are the contents of the SQL History toolbar:

Regarding the SQL History folder, release notes cite this location in Windows 7:
C: \ Users \ your_user_name \ AppData \ Roaming \ SQL Developer \ SqlHistory
Although this folder contains SQL history, it also contains: custom reports and custom fragment files (for example, see 3.1 Sql Developer Release Notes ) Here is my History History folder:

I do not see any documentation for sizing.
Patrick bacon
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