Strech dimensions, objects at a specified angle.
If you're not on Acad LT, you may be able to use AlignSnap.lsp with its AS and ASB commands, available >here<. Use one of those commands, pick the angled whatever object [anything straight], and the crosshairs will align with it. Turn ORTHO On, and you can Stretch [or Move or Copy or...] in the direction parallel [or perpendicular] to it.
Your link doesn't work for me -- Ctrl+Alt+E has no effect, locking into a specific direction or otherwise, when I try it [Acad2020 here]. So you must have something assigned to that key combination, but we can't tell what it contains from your link. I would guess it says simply <90 to lock the direction to vertical [it works that way if I put that into a Tool Palette button]. But without a fixed/known direction, maybe this will work for you:
In the Tool Palette button called "test" below, I put this content:
(strcat "<" (angtos (getangle)))
Then I can grab a grip [note the free direction of movement at first], pick on that button, pick two places on something [the angled Line here] to establish the angle, and the stretching direction on that grip is locked into that angle:
It also works within a STRETCH command, when picked after giving it the start point of the displacement.
If you want to just pick once on something to establish the angle, but after selecting the grip you want to move rather than beforehand with my AlignSnap.lsp routine, it's possible that elements of that could be worked into the Tool Palette button's contents, or maybe the Tool Palette could contain a call to a routine like that to get the angle, not in command-definition form but as a function that could be used within grip-editing -- I'd have to think about that.... But if you're willing to pick twice to set the angle, as with that Tool Palette content, you can do that on anything, and the two points don't even need to be on the same object, if your direction might sometimes be [for example] between corners of a sawtooth building outline or something.
