Trimming/Cutting demos is quite complicated, but possible in theory. To get accurate results, I would have to simulate the entire game up to the new start tick.
This is something I want to look into at some point in the future, right now I want to get version 2 out :)

Logs.tf "cheats" a bit by recording events such as airshots during the game and then writing them to the log.
I don't have that luxury, and detecting airshots would require "manually" parsing the entire demo, which involves basically simulating the entire game in the app.
Nevertheless, version 2 of DemoMan is capable of doing just that (thanks to work done by icewind1991).
That means detecting things like airshots is feasible, and might be implemented later in version 2.

Glad you like it! Apologies if it's really slow with so many demos, I only tested this version with ~300 demos :) .
The new version I'm working on will be many orders of magnitude faster. Stay tuned for that...

Thanks for the feedback!
I'll make sorting and filtering persistent in the next update, and sorting by date should also not be too hard to implement. Ability to sort by class will be possible in version 2.0.

Speaking of version 2.0, here's what to expect:

• Full demo parsing, allowing users to see chat log, rounds info, kill log, scoreboard etc. of a demo
  • This also enables me to supercharge the search and filter features, something like "filter by class: soldier" or "search all marget gardener kills" are possible (not sure about performance on these though, they're not implemented yet)
• Completely re-written backend to speed everything up (I measured 1000x-10000x faster load times)
  
• New UI probably because I felt like it

This is in very active development, but it will take a few more months at least because I also have to finish my bachelor's thesis.
Join the discord for occasional dev updates :)

This issue only seems to affect demos with a "." in the name, and the workaround seems to work so far for affected users.
I'm working on a more permanent fix.

I want to share something I've been working on for a little over two years:
DemoMan is a program that helps you manage all of your demo files!
If you're anything like me, you probably have 'ds_enable' set to 2 to record
every game of TF2 you play, and so you have accumulated a few gigabytes
of demos on your hard drive gathering dust.
With no efficient way to find the demos containing your best highlights,
you'll probably never make that epic fragmovie you always wanted to make.
With DemoMan, you can quickly browse all of your demos to find clips,
add, remove, and edit bookmarks, and free up space by automatically deleting
all demos without bookmarks. DemoMan also has support for loading events
for demos recorded with P-REC for those who need it.
You can also assign tags to demos to categorize them.

If you're not like me, or don't know what I'm talking about,
you should give recording demos a shot. It's a very nice feature
you can use to record all of your gameplay while using much less
hard drive space than shadowplay.
I've written a tutorial on how to set up automatic demo recording. (link)

TL;DR: I made a tool for organizing your demo files.
Check out the GitHub for screenshots and a list of features.

DemoMan is free and open-source software released under the GNU GPLv3 license.
It is available for Linux, Windows and MacOS.

Source code, screenshots and installation instructions are available on GitHub

Join the Discord server

All feedback is greatly appreciated.
Don't hesitate to submit bug reports, suggestions or questions on GitHub or Discord.