Downthemall missing window elements

Unfortunately, this appears to be bug with current versions of DownThemAll and Firefox 55+. The only way I have found to solve this is to downgrade back to Firefox 54.0.1 or earlier.

Note that due to changes in Firefox 57 regarding the adoption of WebExtensions (with FF57 likely being mainstream released around October 2017), DTA will likely need significant rewriting to continue working in the future and it's not clear yet whether or not those updates will occur.

So for now, if DTA is important to you, you may need to keep two copies of Firefox (pre and post FF55) to continue using it for a while.

The problem I suspect brings many here is not simply that DownThemAll's Title Bar is missing, but that as a consequence it is impossible to reposition its window.

When I read in Dan Whaley's question,

I can right click on the left side and get window controls, as well as drag it around

I began to experiment, and discovered that, in my case at least (Windows 7 Pro, FireFox 55.0.3 (32-bit), DownThemAll 3.0.8), there is a portion of DownThemAll's window that can be used in lieu of the Title Bar for repositioning (see my illustration). Note that you can also right-click in this region and select Minimize.