i can't seem to find the settings to fully customize folders where to save files by type.
it randomly works but most of the time it doesn't

It's not random. It works only for folders (libraries) defined in Windows File Explorer: Documents, Music, Pictures and Videos. Other files go to Downloads folder.
Read more about libraries: https://www.google.com/search?q=librari ... ewwindow=1
then try to create your own library folder and see what will happen…

The sorting works with the files defined in Windows File Explorer.
Do you have any specific problems?

i used to be an IDM user.
their Save to... Category is what I'm after.

or setting something like:
File types: *.jpg;*.png;*.bmp;*.psd
Save to: D:\Downloads\images

In FDM 3.x you can define groups - it's even more powerful feature and many users voted to add it to FDM 5.x.

Thanks Usher, but upon fiddling with FDM 3, I find it kind of complicated configuring the settings. Plus FDM 5's minimal interface is a plus.

Anyway, I'll stick with FDM 5 for now and suggest the feature of customizing directories according to file extensions

File type: .doc;.docx;.ppt;.pptx;.xls;.xlsx;
Save to: D:\Downloads\Documents

File type: .jpg;.png;.bmp;.psd;
Save to: D:\Downloads\Images

File type: .mp4;.avi;.wmv;.mkv;
Save to: D:\Downloads\Videos

This kind of suggestion has been mentioned before< wer'e always looking to improve.