I use less version 590 (GNU regular expressions).
I use
export LESSFILE="/root/.lesshst_for_manpages"
export MANPAGER="pager --save-marks -I"
man -L en <<somemanpage>>
... but --save-marks appears to have no effect when setting marks in manuals (using the m command in the pager). When reading the same manual again, the pager does not seem to remember the previously set marks.
What can I do?
When you use less with --save-marks, set a few marks in the file called file, and quit the pager, your ~/.lesshst files will contain a few lines of information about these marks:
$ cat ~/.lesshst
.less-history-file:
.mark
m a 1 6659 /home/myself/tmp/file
m c 1 33259 /home/myself/tmp/file
Here, I've set the a and c marks at different locations using the m command in less, in the file ~/tmp/file. As you can see, the two marks are tied to the pathname of the file. This allows us to view the same file in less at some later time, and go to either the a or c mark using the ' command.
Setting the a and b marks in another file will update the saved a mark and add the b mark:
$ cat ~/.lesshst
.less-history-file:
.mark
m a 1 46559 /home/myself/tmp/other-file
m b 1 13309 /home/myself/tmp/other-file
m c 1 33259 /home/myself/tmp/file
Note that the a mark in the ~/tmp/file file no longer exists.
The point is that the marks are locations in files at particular pathnames.
When you use less as a pager for reading manuals, what is the pathname of the text document you read? You can get this information using either the = command, the :f command, or by pressing Ctrl+G in the pager. A hint: There is no filename.
The reason there is no filename is because the manual, i.e., the text document that less is displaying, is coming from a pipe. It's similar to using less like so:
$ cat file | less --save-marks
... and if you do that, and set a mark, you will notice that the mark is removed from the .mark section of the ~/.lesshst.
In short, less cannot remember a mark in a piped document. This is why marks are not saved when using less for viewing manuals. Furthermore, any marks that you try to set in a manual will be cleared from your ~/.lesshst file.
less reads the data from a pipe, it does not have any information about where the data comes from. How could it have?
man supplying the less pager a string to use as prompt on your system (not on mine). You can do the same with less directly: less -Ps'Hello Silver!' somefile. The actual prompt string used is documented in the man(1) manual. This has nothing to do with the name of the file that less is showing you (it is still unknown to less because it's comes from a pipe, or it's a temporary file somewhere under /tmp). Note that marks saved by the m command are saved with the filename, not the prompt string.
less does not use it. You would have to patch the code to do what you want. It's most definitely possible to change the behaviour of less, but it does not change by magic just because you want it to.
lesscommand which allows marking.