yes, it is a problem for me - its why I started the discussion.
Ok, good that you are able to clear that up for me as I thought I had perhaps misunderstood something during the discussion. Thank you for that.
But I cannot install Lazarus using Fpcupdeluxe on shared folder.
That much was also clear

Do note that using FPCDeluxe on a shared folder that is created by a 3th party software is not really a concern of FPCDeluxe though I also believe that there might be a simple solution that solves your issues. As said, my knowledge on Virtual Box shared folders is next to none (I hardly ever use them) and have never heard/seen of your use-case before.
Workaround solution with install to local folder/rename/move - too many problems - I need to update settings in VirtualBox and in Linux guest under root, restart virtual machine 2 times, copy files to & from. High chance to make error.
Also this will increase VM size and it will never decrease even if I delete folder where it is installed
I am not sure why you need to take all those actions but it is also not relevant for your issue.
The dynamic growth without automatically shrinking after deletion is something I am familiar with and Virtual Box offers tools/extensions to 'resize' your virtual HD if you really want to (though I would advise against it as the risk of corruption can be very high, which in itself causes more harm than it solves). It also requires for you to take additional steps so adding more actions to try and solve 'the problem'.
Comparing with - start Fpcupdeluxe, press 1 button, close.
Give the VM you use to build FPC/Lazarus some extra memory and allocate that for a ram-disk (pretty much a standard exercise on Linux) and use that as a HD. Download FPCDeluxe to it, run FPCDeluxe with the "one button action" and take one additional step: copy the result that FPCDeluxe created to your shared folder.
do you suggest to create local folder for Lazarus installation using ram disk, in order to prevent VM to grow in size?
Not creating a local folder, mount an amount of ram as "HD" and literally use that as a HardDisk. If you want to create folders and what not then be my guest and pleasure your hearts desire but it is not needed. As written above run FPCDeluxe from it and store the result to that drive as well. FPCDeluxe let you choose/select where to want to install.
And yes because it is a disk made in ram it will not (at least should not) increase the size of your VM (with the catch that if FPCDeluxe somehow install dependencies for the OS then it will (still) grow).
This is workaround to workaround.
You are the one suggesting using a shared folder for your FPC/Lazarus installation. My only suggested workaround is to mount a ram-disk and copy the final results to your shared folder.
All other problems will remain ..
No, they will not. Not sure how I am able to convince you otherwise unless you try for yourself. Also here is a catch: if you have installed FPC/Lazarus in your shared folder using the 'old' methods, does it then work for you ? if yes then my suggested ramdisk workaround is able to provide the same.
You know what a normal use case is for Virtual Box in such situations ?
Add another VM, install something like FreeNAS and use that as a storage device. For every VM that you want to have access to FPC/Lazarus also fire up the FreeNAS Vm and (auto)mount the network shares where you have installed FPC/Lazarus.
I would even go one step further and create a build server VM that is also able to host the compiled results. Those are 'normal' use cases (not suggestion there is anything wrong with your use-case, it just sounds a bit odd for/to me).
But this topic is drifting further and further (in)to virtual Box and not FPCDeluxe.