I'm trying to create a new custom tab via setup -> appsetup -> create -> tabs. How can I get the exact count for the custom tabs, because I can see only 18 tabs, but it throws an error about the custom tab limit being exceeded?
Click on Setup, then scroll down to the "Monitor" section and click on System Overview, you will see the limits on the right hand side. Custom Object Tabs, Web Tabs and VF Tabs all count against the limit. Tabs that are from public managed packages from the App Exchange, do not count against the limit. (The tabs with the managed installed icon, should not be counted).
You can use this in workbench to get the tab metadata. please make sure to run this as a System admin.
It will give all information related to tab in your org. Hope it helps. thanks.