(by Andrzej Rzoska)
ChainTrim, a command from ChainTools toolkit, uses an innovative approach to make trimming operations in Rhino easier and more controllable.
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Currently, ChainTools consists of one command: ChainTrim. In ChainTrim you interactively build a set (chain) of trimming curves on an object to be finally trimmed.
When picking the curves, you have control of how the trimming chain will look like, which intersections, edges or curves it will include.
The command checks and warns if there is no continuity between the curves or to an edge of the trimmed object. It also allow you to extend the curves on the trimmed surface.

To use ChainTrim, simply type "ChainTrim" in the command line.
 The plug-in (which is currently Work in Progress) will run for 90 days counting from build date.
 At the end of the expiry time (or sooner), expect a new version to download, with new 90 days to utilize.
 See also videos available below.
 I am planning to add new commands based on assembling curves into chain, at first it will be ChainSplit.

 If you try out ChainTools, your comment on this site will be welcome :-)

New version is available from 27-02-2021:

- Extend subcommand works also on edges in way of reflex angles (ExtendCrvOnSrf can't do that)