I can copy a plugin keyframe from the timeline but Im not able to paste it. Is there any possibility to do so?
Please, look at the Keyframes: Copy and Paste tutorial:
It just doesnt work at my installation.
Very curious. 
Please, show a screencast for that. Open the Overlay window becasue it is important to see the set for that.
You can upload the video (screencast) on https://files.fm (no need registration) or where you prefer.
What Cinelerra-GG version are you using? (and Alternative shortcuts)
I dont have a routine for screencasts. It would take me great effort to make one.
I will try with screenshots.
You see my Overlay window.
When I right-click in the timeline on a golden key to copy a keyframe, Im not able to paste it anywhere on a (disarmed) track.
Also it doesnt work when I press shortcuts Shift-v, Alt-v - or when I do it via the menu Keyframes
Installation
Though Im on debian 12 I use the cin version from the debian 10 repository: deb https://cinelerra-gg.org/download/pkgs/debian10 buster main
edit: cin version 1:5.1 20201031
I have to add the buster repos too because there are dependencies.
It somehow installs then (without errors finally). But of course not satisfaction.
I cant even tell you which version of cin I have. It is one solution to get it somehow running.
Because I use LXDE I havent been able to open these appimage versions. You cant just click on it to open on every window manager like LXDE/openbox as it is advertized often.
Si Im somehow stuck here. Perhaps I should compile a version. But I dont even find the source.tar.gz
2024-07-07-103511_1920x1080_scrot.png 2024-07-07-104155_1920x1080_scrot.png
I think that the Keyframes: Copy and Paste tutorial is clear: Copy and Paste Keyframes work fot the Armed track/s, and there is the own reason.
You must Arm the track where you want to copy from, and then Arming the track where you want to paste in to.
For screencast (screen recording video) I use RecordMyDesktop. Maybe you can install the same, or OBS?
Sorry I just messed up armed and disarmed. I of course paste into active tracks (green).
If I want to paste on the same track and the same effect but 20 frames later this arming and disarming should not be necessary.
For standard keyframes it works as expected (copy from green track and paste into new green track)
But not for the golden keys.
1:5.1 20201031 is my cin version
I think I got it.
It probably was an out point far beyond of the last clip.
Sorry I am not expert on Linux.
Have you tried to download this version?
https://cinelerra-gg.org/download/images/CinGG-20240630-alternative_shortcuts.AppImage
Is your Operating System that doesnt permit to use AppImage?
I am testing your issue on UbuntuStudio_16.04 (year 2016) using cinelerra-5.1-ub16.04-20201031.x86_64-static.txz.
The screencast shows HistogramBezier plugin and Copy and Paste Keyframes. It works!
Sorry, for time problem you have to download the ogv file to see the video: https://files.fm/u/9t26enry8n
I made the mistake to have an ] outside of my clips.
There the golden key has been pasted to. It was not visible to me so I thought the pasting process wouldnt work.
The appimage problem is not a problem of the distribution itself but a problem that not every window manager can handle it.
I was wrong.
It seems I can open appimage meanwhile.