In SmashFlyX, you can concatenate folders and move folders
To create a subfolder, go to the main folder you want. To the far right will be 3 dots. Select this and a menu will open to create a subfolder:
Select Create Subfolder. This will take you to the folder creation window.
Put in the folder name and select Add. This will add the folder to the main folder and you can see this as an arrow will appear on the folder. Selecting this arrow will open up the folder concatenation.
Similar to the above, select the 3 dots to the far right of the folder you wish to move and select Move. This will open the Move window.
Type and choose the folder you wish to move to and select Move. This will then move the selected folder to the new folder concatenation.