The Media Assembler Node (introduced in v2.5) can be used with AVI and MPEG2 files to merge clips/reels into one single clip and is ideal for such tasks as topping and/or tailing clips with credit sequences or bars and tone.
To use the Media Assembler node, select it from the tools in the workflow builder and create a new template for it.
A simple menu appears that allows you pick a clip or reel to add to the beginning and/or end of any clips the tool is applied to. Just click "Pick" to open the file browser and select the file you'd like to use. (Note: Only AVI or MPEG2 clips are currently compatible with this tool)
Once you have picked the clips/reels you'd like to use, name the template and click "save"
Now the Media Assembler node can be dragged into the workflow builder and template selected. Next add a Platinum node set to the format of your desired output, then any other workflow tools that you require. Save the workflow and from now on, any clips or reels you apply it to will have the clips/reels picked in your template combined with them.