I estimate that TST, all by itself, nearly doubles Firefox's memory footprint. Sidebery freed up 5-10G of memory for me by comparison (yes, way too many tabs...). TST should *not* be a recommended extension. Latest update of TST leaks memory *very badly* and crashes, taking other Firefox extensions and other desktop programs down with it when the OS starts killing things to free up memory. Sidebery is *much* more responsive & performant with a very large number of tabs. This alone will remove a huge amount of friction in reducing the number of open tabs. No more waiting for TST to catch up. Switching to Sidebery was no problem: all nesting retained. Disable TST. Install Sidebery and verify ok. Remove TST. Done.