Installing via DIM still puts the files were the DIM wants to, not over the top of the existing install. I suspect I’ll need the ‘old trick’ of installing the standalone exe and persuading DIM that it’s really there
Install Manager has no knowledge of that which it did not install. It never has and we have never claimed otherwise. In fact we have been very transparent about this, quite intentionally, from the very beginning. There is simply far too much variability in what has been done to/with files for Install Manager to produce a consistent/reliable experience for them.
It should go without saying, but I will anyway, that any “trick” to “persuade” Install Manager to behave in a manner other than it was designed to is not guaranteed to yield the result you are after. The application was designed to function in a particular way. A way that produces a consistent and reliable experience. Those attempting to be clever should [inherently] understand that they are responsible for their results… both desired and otherwise.
Install Manager allows you to specify the base path(s) for the applications it installs; one for 32-bit applications and one for 64-bit applications; Settings (cog icon, upper right corner) > Installation page. Each application package is then responsible for providing it’s own relative path that Install Manager will append to said base path(s). That relative path is plainly visible from the “Ready to Install” page, using the “Show Package Files…” action in the context menu (right-click) and option menu (far right arrow) of every single package. Those two very basic, very simple, things (i.e. base path and relative path) are what determine where Install Manager will install the files of any given application. There is no “trickery” involved.
Often times an application is dependent on the existence of supporting libraries and/or configuration files which need to install to specific areas of your computer (as determined by the operating system and/or library provider), so the package will include those as well. And like the application files listed in the “Package Files” dialog mentioned above, so too are these system dependent relative paths.
In so much as a particular application is supported by Install Manager, when an application is installed by Install Manager an entry for that application (version and bit architecture specific) is added to the Settings >Applications page, for the current account. This entry is then used by application dependent extension packages (i.e. plugins, shaders, content that installs like a plugin, etc.) to know where to install to. If you did not use Install Manager to install an application, and you haven’t manually added said application (version and bit architecture dependent) to the list, Install Manager does not know where it should install those types of packages. If you are going to mix installation methods (i.e. standalone installer for the application and Install Manager for add-ons), you will need to become familiar with how this works because the application cannot do it for you (as it does when you just use Install Manager).