Managing your Toolbox is simple. Navigate to the tab on the top of the page that says Workspace. Head down to the sub-tab menus on this page and find My Toolbox. Here you will find all the tools in your toolbox. To remove a specific tool from your toolbox, find the grey 'X' and tap on it.
You can also remove a tool from your toolbox in the tool detail page of the specific tool you would like to remove. Find the gray button 'Remove from Toolbox' and tap on it. Just like that, you have successfully removed that tool.