Geany Portable Plugins (at "https://downloads.sourceforge.net/geanyportable/Geany_Plugins_0.20.paf.exe" referenced on the PA Geany Portable page)are not binary compatible with the current Geany Portable executable(linked from that page, "https://portableapps.com/apps/development/geany_portable") and must be recompiled, per the message log from Geany upon attempted installation of the afore-mentioned plugins.
The link to the plugins should be deleted with an explanation that there is no plugin support or it should point to a recompiled, compatible version. FYI, Universal Extractor (version 1.6.1)could not extract the files from the windows setup exe (no zip available)for the plugins from the Geany.org site ("http://plugins.geany.org/downloads.html").
I found a nightly build for windows, that have the executable and a subdirectory for dll plugins. That solved for me, the lack of access to compatible plugins. Now my version is 1.23 (git >= da78a44). Was compiled Nov 19, 2012.
Unfortunatly, as good as Universal Extractor might be, it isn't kept up to date and can fail if it runs into something it doesn't understand.
I downloaded the file you mentioned, and successfully extracted it using 7-zipFM version 9.22.
There are two possible failure points in your case: Universal Extractor might not see the file as a 7-zip archive and as a result calls the wrong unarchiver, or if it does correctly ID the file, it might not be using a current version of 7-zip.
neutron1132 (at) usa (dot) com
Some installers can be expanded. These are those with a little sphere as an icon.