There's a couple of ways to achieve the outcome with smart walls. The screenshot below shows something like what you're after with the T-intersection being done either by using the Architect/F2 Edit Walls/S1 Clean/Cap then turning off Cap leaving Clean on and by Area select the end of the horizontal wall as it trims to the vertical and it should clean as shown in the second down horizontal wall. The other way is to ctrl-right mouse click towards the end of the horizontal wall you want to trim to the vertical which opens the wall properties menu. Toggle of Cap and pick apply then close.
When there's multiple different wall types converging, especially at a corner wall it can still be done but may take 2 -3 or cleanups to 'rotate' the outcome until you get what you want. All three walls have their end caps off and using both 1-line and 2-line trim the outcome can be achieved. Another way could be to extend the vertical past the two horizontal walls, ctrl-right click to turn off the end caps, the 1-line trim the vertical back to align with the horizontals. Once done you can also stretch any wall to any angle and the cleanup should still maintain itself.
You can also press Shift and the | keys when drawing a smart wall to toggle off/on their end caps on the fly.
Just looking at your screen setup, if you open the Tools pulldonw/Program Preferences/Toolbars tab and at the bottom left, Status Bars adjust the value this will widen the smart entity menus so you can see them better. Mine is at 84 for 27" monitors so you'll need to play around to suit your own screen.