In order to import a custom character you need 2 things: the preset file (.preset and .preset.expreset.xml if it has custom wideslider values) and the required mod files if any. Both preset files go in the Preset folder. Mods go into Mod folder.
Not all presets require mods. Those are called vanilla presets because they only rely on official dlc.
For those that do require mods the preset uploader usually bundles only the mods that they made themselves or not even that. If you're lucky they left a note in the readme or some screenshot with clues for what mods were used. With some more luck these mods still exist and are available for download but probably behind some twitter password.
Preset files can be inspected in SybarisArcEditor to see which menu files they require. The menus marked in red are missing or are assets from CM. SAE can't look for CM asstes in COM because they are in a separate Gamedata_20 folder. SAE only looks in Gamedata. You can search for the menu name
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to find the mod source.
Then of course you can run the maid editor and load the preset to see if it works right. You might need to hit F5 and enable WIDESLIDER. I think it's turned off by default. If you don't know what I'm talking about then install
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and read the documentation. CMI by default installs the "Basic" configuration which does not include the AddModSlider plugin (aka wideslider) required for custom presets. You'll have to use another configuration preset such as "Similar to Noctsoul AIO" which was the standard back in the day.