Hello,
I am not sure if I understand your question correct, but there are some options how to use debug shell by command line in S32 Design Studio.
1) The simplest way is to start S32 Design Studio IDE and connect to some board. After the program is loaded, you should see the following screen. Click on the arrow in the red box and choose powerpc-eabivle-gdb. This is gdb client debug console, which is used for executing gdb commands.

Write help to show list of classes of commands.

It is also possible to create scripts. I am not experienced in this area, but look at the following URL where you can find some useful information. Also if you use google, you will find many useful pages about gdb commands and scripting.
https://sourceware.org/gdb/onlinedocs/gdb/Command-Files.html
2) There is also a possibility to use gdb server and gdb client without S32DS IDE. You can run gdb server directly from command line (C:\Freescale\S32_Power_v1.1\eclipse\plugins\com.pemicro.debug.gdbjtag.ppc_1.3.3.201605241936\win32) and connect to the board you want to debug.
Then you run gdb client (C:\Freescale\S32_Power_v1.1\Cross_Tools\powerpc-eabivle-4_9\bin\powerpc-eabivle-gdb.exe) and connect to the running gdb server.
If you ask about tcl scripting the answer will be no. Tcl scripting is not supported in S32 Design Studio. But there is another option about scripting. If you have installed S32 Design Studio for power version 1.1, there is possibility to run .mac scripts.
Click Debug configuration->Debugger->Advanced Options

Enable Initialization script and choose the script you want to run. This script is run during initialization phase.

Executed script you see in the picture above is hard-coded (it is executed all time, but it can be changed the content of the script). When you use your own script, it should be also executed in this phase.
Regards,
Martin