Option --altern?alternate-target-paths is not supported and will be ignored

Thanks to all the developers and the Forumexperts!

This is my second time trying to use duplicati.

I create a local backup using Duplicati - 2.0.4.23_beta_2019-07-14

I back up to local folder or drive:
T:\Duplicati_10_2019?altern

using --alternate-destination-marker and --alternate-target-paths but I get the title error in my log when I try to use these options.
Also the advanced options apparently completely disappear when going back in and wanting to edit them later.
The only trace I see is the added “?altern” at the end of the path.
My alternate-destination-marker seems completely lost.

The post by grossepointblank
is unrelated as this person apparently was trying to mark an alternate source; but I am trying to mark a alternate target.

Under command line I find the Target URL:
file://T:\Duplicati_10_2019?altern?alternate-target-paths=*%3A%5CDuplicati_10_2019&alternate-destination-marker=Charles_10_2019.txt

Perhaps this string has a problem?
However, %3A is the “:” and 5C is the backslash “”
To me that looks as intended.
Perhaps the duplicate appearance of “?altern” could be the root cause? But, I did not put this there, I just used the dropdown options seen in the image.

Please advise?

while editing the Configuration in the web page If I put the full path with the two advanced options as

T:\Duplicati_10_2019?altern?alternate-target-paths=*%3A%5CDuplicati_10_2019&alternate-destination-marker=Charles_10_2019.txt
and then click [Test Connection]
I get: “Success
Connection worked!”
message box.

I clicked 4 times [Next] then [Save]

We will see if the warnings disappear and the backup still works if the drive letter changes.

I’m not sure it’s the same, but this reminds of of ?auth-u automatically added to destination path where extraneous characters were added, and you have roughly the right number of them, and then they end. The suspect code is shown, but I forget if an issue was filed. Feel free if you have steps to reproduce it.

I went to Home => configuration edit=> [next] => Browse =>Manually type path
Then I removed the extra characters to obtain “T:\Duplicati_10_2019”
Test connection is success with or without the last “” I left it in
=> 3 ea. [Next] [Save]
Close all browser windows.
Trayicon [Open]

Home => configuration=> Export=> to File
Results in a JSON file that does not contain “altern”

If I then
Home => Run now
I will observe the two log locations:
Home =Reporting => show log
About => Show log

If the warnings and errors are still there.

Then I will try once more using the alternate drive letter and alternate markings.
With and without the apparent extra letters.