As above the planner can only be used for NDL dives. To plan dives you need to use the Suunto DM5 planning software (download from suunto.com). You can after planning then upload the plan into the computer. I dont know just how it works as I never do that. My deco dives are planned on DM5 and noted down only. I use Eon Steel Black with Gradient Factor algorithm which is not available for Eon Core. The Core uses "Suunto Fused RGBM". At the top right on the planner there is a dropdown list of available algorithms, so in your case it is important to select Fused RGBM. Be careful to select all the correct parameters as well such as sac rates, tank reserve pressures, sizes, pressures etc so your plan will show gas consumption against time to indicate you if can perform the dive within your parameters. I would also download the manual as there are good explanations of deco windows and either a stepped traditional deco profile, or a continuous deco profile, ascent rates and penalties for ascending at more than 10m/sec for more than 5 seconds ( adds extra stop time).
Hope this helps and happy diving.