Context: main0201.xhp par_idN10855 <image id="img_id3174230" src="cmd/sc_extendedhelp.png" width="1cm" height="1cm"><alt id="alt_id3174230">icon What's this?'</alt></image> location of the file: https://git.libreoffice.org/help/+/master/source/text/shared/main0201.xhp#0
Olivier/Sophie: comparing with similar cases, eg: source/text/scalc/guide/scenario.xhp:55:<image id="img_id1593676" src="cmd/sc_navigator.png" width="0.1665inch" height="0.1665inch"><alt id="alt_id1593676" xml-lang="en-US">Navigator icon</alt> source/text/scalc/guide/scenario.xhp:60:<image id="img_id7617114" src="sc/res/na07.png" width="0.222inch" height="0.222inch"><alt id="alt_id7617114" xml-lang="en-US">Scenarios icon</alt> source/text/schart/01/type_xy.xhp:105:<paragraph role="paragraph" id="par_id56635427" xml-lang="en-US"><image id="img_id56635427" src="chart2/res/step_center_y_30.png" width="30px" height="30px"><alt xml-lang="en-US" id="alt_id56635427">Center Y icon</alt></image></paragraph> I'd put: What's this? icon but no strong opinion here, you decide! :-)
Olivier Hallot committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/c3eb8a242ee732d6789310b5a9dd0bf10b5a4c6a tdf#147136 Fix help entry for "What is this?"