Best place for would be in the Feedback session.
The tools that UE4 provides (including the “level design” tools) are some of the best in the industry. 90% of all use other software, such as Maya, to do all of their designs. Many even use the “paper map” technique which involves actually drawing out the layout of the map on paper. You should consider doing all of your level designing outside of the editor before you do block-outs in BSP. BSPs are used to test the map out and allow for quick changes without requiring reimports.