To quickly switch between plans, press and hold (long press) the background of the Detail screen; a small window will pop up showing the first five plans from the Settings | Reading Plan screen. If the plan you wish to switch to isn't visible, simply move it into the top five in the Reading Plan screen.
This feature will adjust the start date of a plan so that the the first incomplete reading is today. Select a plan in Settings | Reading Plan, back out to Settings, then tap Adjust Start Date Unless you're exactly on schedule, you will see the Start Date. change. Your Progress will not be affected.
Reading plans can now specify alternate links for particular readings (by appending ">2" to indicate a secondary link, ">3" to indicate a tertiary link, etc.) A example use case is linking OT passages to a Hebrew bible and NT passages to a Greek bible.
As always, the primary (default) link for the plan will be the one selected for that plan in Settings | Bible Link. Place the secondary link for the plan directly underneath the primary link (and the tertiary link under that, etc.) If you have multiple plans with multiple links, it may be be necessary to download an extra instance of a bible link to get the desired ordering.
This is an advanced feature; please contact support if you have any questions.
New features in prior verions (4.0 and later) are described here.