Docs: Macro right-click menu.

doc/4-instrument/README.md

@@ -126,14 +126,25 @@ finally, the sequence of values can be directly edited in the text box at the bo
 - in arpeggio macros, a value starting with a `@` is a fixed value as described above.
 - in bitmask-style macros, the values are added up in binary and converted to decimal. see [the hexadecimal guide](../1-intro/hex.md) for more info.
 
-
+in all cases except bitmask macros, right-clicking on the graph opens up an editing menu:
+- **copy**: copies the macro.
+- **paste**: pastes the macro in the clipboard.
+- **clear**: clears the macro.
+- **clear contents**: resets all values to 0.
+- **offset**:
+  - **X**: slides the data "horizontally" within the macro, filling the gap with zeroes. data moved past the start or end is lost.
+  - **Y**: increases or decreases all values, clipping them if they would move past the allowed range.
+- **scale**:
+  - **X**: stretches the macro.
+  - **Y**: multiplies all values by the scale factor, clipping them if they would exceed the allowed range.
+- **randomize**: replaces all values with random values between **Min** and **Max**.
 
 ### ADSR
 
 ![ADSR macro editor](macro-ADSR.png)
 
 - **Bottom** and **Top** determine the range of outputs generated by the macro. (Bottom can be larger than Top to invert the envelope!) All outputs will be between these two values.
-- attack, Decay, Sustain, SusDecay, and Release accept inputs between 0 to 255. these are scaled to the distance between Bottom and Top.
+- Attack, Decay, Sustain, SusDecay, and Release accept inputs between 0 to 255. these are scaled to the distance between Bottom and Top.
 - **Attack** is how much the value moves toward Top with each tick.
 - **Hold** sets how many ticks to stay at Top before Decay.
 - **Decay** is how much the value moves to the Sustain level.