There are different selection tools in MarvinSketch. These are as follows:
Rectangle Selection: The default selection tool. Hold the left mouse button while selecting and release the button when you are ready.
Lasso Selection: Hold the left mouse button and move the cursor around the fragment. Release the button when you are ready with the selection.
Structure Selection: Single-click any atom of a structure to select the whole structure.
Lasso Selection and Structure Selection can be chosen through a drop-down list.
To select an atom, bond, or group, use the Rectangle Selection or the Lasso Selection mode (single-click, drawing selection area).
To select a structure, use Rectangle Selection or Lasso Selection mode (double-click any of its atom or bond), or Structure Selection (single-click).
To add more parts to a selection or remove parts of a selection, hold the Shift key while clicking on the desired parts.
To invert the selection, for example, to select everything previously unselected, use Edit > Invert selection (Ctrl+Shift+I). If nothing is selected on the canvas, this action selects everything on it.
To deselect, click on an empty place of the canvas.