Both Bookmap and NinjaTrader can chart price levels from a worksheet that is hosted online. This allows you to create a google sheet, publish it to the web, and then when you edit it, Tradovate can pull the price levels and then chart according to symbol and price. I currently have NT8, and it can update as quickly as 5 minute intervals.
Tradovate can’t make external api calls from the indicators. You can kind of do this manually by having an indicator that draws lines. It is tedious compared to the solution you request but works.
I do have a paid indicator that that basically does this. The data for the lines would be part of the code itself, in an array. The format function in the spreadsheet creates the entries for the array. You would then copy the data entries from the spreadsheet, open the indicator code in Tradovate, and paste entries into the array.