I've been wondering if this networked drive issue has been resolved. My external drive is networked but not mapped, meaning I have not assigned a drive letter to it. I use a laptop so drive mapping doesn't make much practical sense. I usually connect to the drive via the "Network" icon and then select the drive. My connection to the drive looks something like this:
\\LS-GLF6E\share\....

The problem is that UEStudio (the most recent version) doesn't display my "Network" (nor the drive itself) in the Explorer Tree view. So I always have to open very manually and it seems it takes forever (and even then the UES doesn't put the drive in the tree). On the same laptop I have also PSPad and EditPad Pro and both display the network icon in its tree and it opens the files from the networked drive almost instantly.

So I am wondering if this is something that IDM is working on to improve or maybe there is a way to enable a more complete tree view that I missed somehow.

I don't have any delay opening a file using an UNC path. I suggest to use Filemon from SysInternals to log all file accesses while you open a file in UltraEdit with an UNC path. Maybe you can see in the log what is the reason for the delay. My experience with such delays is that a security setting is the problem.

The Explorer tab in the File Tree View shows only drives and none of the virtual folders Microsoft has defined for Windows. I use also a laptop at home, in the train to/from work and in my company. To solve the problem with mapping the network drives only when I'm in the company I use a batch file like this:

@echo off
if not exist "\\computer\share\dir\file that always exist" goto !EndMapBatch
net use drive letter: \\computer\share /persistent:no
:!EndMapBatch

This batch file is executed on startup of Windows with a shortcut located in the "Startup" folder of the Windows start menu. In the properties of the shortcut I have selected to run the batch file with minimized window. Of course I can click on the shortcut to run the batch file also when I started my laptop in the company without network cable plugged and later plug it and need the network drives.

You could also configure in UEStudio a user tool with just the "net use ..." command line to map the drive from within UEStudio when you need it.

Thanks Mofi! I think I'll use your batch file suggestion since it seems it works fine. How I've been using the UNC path so far is to define it in "advanced : configuration : directories" and then specify the UNC path in the default open directory field. No delays. And then at work I'd use the File Tree view. However, when I need a virtual drive at work then I need to reconfigure the default open or use PSPad for quick editing. Anyways, your batch file seems to be the solution!