You can import a previously saved ACP plan back into Planner for editing and re-saving by choosing, in the File menu, Import ACP Plan. Select the plan file and it will import, populating all of the fields and options. After you make changes, save it as you would a newly created plan.
Since ACP observing plans can contain many features that are not supported by Planner, you should normally import only plans which were previously generated using Planner with the same preferences. If you do import an arbitrary plan, Planner will do its best to check for problems, and in some cases it will refuse to complete the import. Read on for issues relating to things like timing of observations.The import process checks for incompatibilities and errors in the plan, and if any are detected a Notepad appears listing those issues.
If you typically use Planner's timing features, the plans you import will contain #waituntil directives that control the timing of observations. If you have the "reusable plans" option turned off so that full dates and times are used, the date/time in the plan will be in the past, usually by a day or more. As Planner imports the plan, each of these times will be advanced individually by a day at a time until they are in the future. Thus, be careful when you import a plan! The best time to import is during the day (at the observatory).
Also, if your imported plan has any target(s) whose start time(s) are before the end of the previous target, those targets will fail to import. Thus, if you make any manual adjustments to times in a plan after generating it, and those times conflict between targets, you'll run into problems importing. Since you can edit in the Planner now, that's the best tool for making timing changes. You get the benefit of ripple editing too!
There are several things you need to be aware of when importing ACP plans. Most of these arise when your current observatory profile (preferences) are different from those that were in effect when you saved the original plan that you imported. The following things will cause the plan import to fail with descriptive info in the Notepad that appears:
In addition, some of the directives that appear in Planner-generated plans (such as those related to auto-focus) come from preferences settings. When saving an imported plan, these directives will be replaced with ones that are specified by the currently loaded profile (Preferences). Finally, if the imported plan was produced when Flat Planning was active, and thus have specific flat plan files, these will be ignored and replaced with newly generated flat plans when the plan is saved. This allows any edits to the plan to be reflected in the (newly generated) flat plan.