I created an account specifically to rate this app and to tell the dev how awesome he is. The lack of this addon has been a major gap in Seamonkey's usability until now.
Thankyou dev! Although this addon is quite basic and lacks indents for child tabs, it's still a wonderfully useful extension and might be the catalyst to make me switch back to SM from Pale Moon.
I really hope the dev continues to maintain this extension and adds features like indents for children and... that's about it! It's no Tree Style Tab, but it's a very welcome addition to the Seamonkey ecosystem.
SeaMonkey users have long yearned for vertical tabs and apart from rumors that TST once worked with an ancient version, the browser has been bereft heretofore. Vertical tabs are of the killer add-on class for many users, and this has previously prevented many an inquiring mind using Firefox to switch over. Though I wish this could be a port of TST instead of the simpler VertTabs, this is through no fault of the developer who has done an excellent job and answered the masses clamoring for tabs on the side. I can only hope they will keep this add-on updated so that SeaMonkey will remain more viable. If you ever feel like asking for donations, I would gladly give $5.
This vertical tab add on is an excellent addition to the Sea Monkey collection of add ons. For a person who uses several dozens of tabs, on a daily basis, it eventually becomes a chore, to move from one tab to another one, when they are lined up in a horizontal fashion, as usual. Instead, a vertical tab add on allows the power user to scroll up and down quickly, and locate the tab he or she needs, much faster than when they are lined up horizontally. I say this, because when the pointer hovers over a tab, a large thumbnail of that web page appears next to the tab itself. This add on also allows deletion of tabs, using the mouse. So it helps the power user to efficiently remove clutter.