Hello Howardlong, thank you very much it works flawlessly!
If you are interested, please find the issue I had below.
As it appears to have affected other DSO5012A users I will make a new posting referring to this posting hoping to help them out.
Recently I obtained an Agilent DSO5012A. Installed options were mem8M, PWR, SGM, LMT, MST and E00.
The seller warned me not to update the SW as I might lose options as others had experienced.
The SW versions were: Boot 03.05, System 06.16.0001, Language 04.10, Library 02.25 and Graphics 02.19.
According to the Keysight site, System and Language were not up to date. Language updated without a problem to 06.16.
Then I took the gamble, updated System to 06.20.0000 and sure enough lost my options: only MST and E00 remained.
Reverting back to System 06.16.0000 did not bring the options back.
The topic "Agilent MSO 5000/6000/7000 - anyone hacked these scopes?" by dfnr2 also discussed the possibility of enabling options (licenses).
Reply #224 from mikeselectricstuff was my first clue for System version 06.16.0001 by unpacking, modifying and packing it again.
Reply #467 from berk98 addressed System version 06.20.0000.
This was all for the MSO series but as MSO was an option in the DSO series, I figured it would also work for the DSO variant.
The link for the unjzp and packjzp tools was not valid anymore: finally found them (aglt-master.zip) on github but not being very proficient in manipulating SW, could not make them work.
In a more recent reply (#606) by Orange I found jzp_0.2 which is apparently based on earlier work from flowswitch and miek but could not make it work either.
So I finally asked if and how that would work using Windows 10.
There was a promt reply #674 from Howardlong and that worked without a flaw.
I may not have done it the most efficient way but for those who ran into the same issue, here's how I dit it.
1) Created a similar folder structure (G:\source\hp\5012A\jzp_0.2) on a bootable USB drive, placing the latest (version 06.20.0000) sys6000.jzp file in the jzp_0.2 folder.
2) unpacked it using unjzp.exe to sys6000.bin file.
3) Selected sys6000.bin in a trial version of a hex editor and opened it.
4) Moved to line 002e80f0, clicked column 08 and entered the new value per reply #467. Note: the editor moves automatically to the next column, enter the new value and so on.
5) Saved the modified file.
6) Packed the modified file using packjzp which yielded sys6000.new.jzp.
7) Copied sys6000.new.jzp to another USB stick, deleted ".new" from the filename, connected it to the oscilloscope and installed the file.
After the automatic restart all original options had been restored!
Kudo's to all people who have made this possible!