Seeking Help with XnView's Instance and Tab Management Behavior

[lindsaymakesvideos]

XnView is behaving in a strange way that I believe is a setting I have wrong somewhere. Here is the current behavior and what I want it to do instead:

What's currently happening:

If I'm looking at folder of images in a file browser, and I double click on that image to open it, it opens in XnView in an entirely new window/instance. So if I open five images throughout my work session, I will end up with five open instances of XnView. (Image attached - "current.")

current.jpg

What I want to be happening:

If I'm looking at folder of images in a file browser, and I double click on that image to open it, it should appear as a new tab in my current XnView instance. So if I open five images throughout my work session, I should end up with one XnView window with five open tabs. (Image attached - "desired.")

desired.jpg

This is the behavior I expect from most apps like this, plus I haven't seen any other complaints about this, so I think it's a setting I have wrong, but I found nothing useful in the Tab section in settings. (Image attached - "no instance setting")

no instance setting.jpg

So what's wrong here and how do I fix it?

--
Additional current annoyance:
Every time I open a new instance by double-clicking on an image in the file browser, that new instance displays whatever the tabs were from my previous session. In other words, by the time I open the fifth image in that example above, I'm looking at five instances, each with the same lineup of irrelevant tabs, instead of tabs I want. Sometimes I will close the unwanted tabs, but when I double-click and open another image from my file browser, they will reappear - continuing the frustrating trend of always having tabs I don't want and never having tabs I DO want.

Because of all of this, every time I use XnView to explore images, I end up having to close up to a dozen irrelevant tabs and windows. (image attached - "annoying.")

annoying.jpg

P.S. - If you're wondering why I use an outside file browser and don't just stay in XnView, it's because of another problem with XnView - I need comparison side-by-side view, and XnView doesn't appear to be able to show me two different folders side by side, I have to choose one or the other. If this is also a setting I'm missing, I'm interested.

[user0]

Settings > General
☑ Allow only one application instance
Save session on program exit - Never

I need comparison side-by-side view, and XnView doesn't appear to be able to show me two different folders side by side, I have to choose one or the other. If this is also a setting I'm missing, I'm interested.

not possible

[lindsaymakesvideos]

You are my favorite person on the planet right now! Usually I have to clarify myself like five times before I get the answer - you made my day! Thank you!