Note that in EasyEDA Std you can only have one PCB design in a project. All schematics in a project are converted to that one PCB. If I understand your usage case correctly, you wish to place several instances of a PCB design (call this A) into a main PCB (call this B). If that is correct then the way to do this is to save A as a PCB module. Then open PCB B in the editor and place as many instances of PCB Module A into PCB  B as you require. To make sense of your schematic then you need to do the same thing by creating a Schematic Module for A. Then place the requisite number of instances of Schematic Module A into your Schematic for B. Please read the Tutorial sections about Schematic and PCB Modules carefully. You may also find that one or more of the extensions from: [https://easyeda.com/forum/topic/Extension-User-Extensions-for-EasyEDA-Summary-9e065b68316f4491a3911dc6204be31e](https://easyeda.com/forum/topic/Extension-User-Extensions-for-EasyEDA-Summary-9e065b68316f4491a3911dc6204be31e)<br> <br> may help. If however you wish to simply place a daughter PCB onto a mother PCB as a plug-in or soldered on component then you must create two separate projects, one for the daughter PCB and one for the mother. In which case your question about component prefixes does not arise. If you want hierarchical design then EasyEDA Pro may be more useful to you.

``` Fireman, thank you for your information. Indeed I do not have a pro version but a stud version of EasyEda. I understand that there is nothing else to do than that after placing several of the same prints on a master printed circuit board, I then have to take the time to number the consecutively numbered items back to the numbers of the original first print. Doing this on that way always I get the message that the item already exists, but that it is allowed to do so. I have to deal with it. Regards Peter ```

Sorry for the mistake in your name Andy!