The active sequence strip is displayed with a light outline.
The entire strip could be selected by clicking LMB in the middle of the strip.
The Select Menu helps you select strips in different ways.
Selects all the strips in the timeline.
Deselects all the strips in the timeline.
Inverts the current selection.
Box Select B
Click and drag a rectangular lasso around a region of strips in your Sequence workspace.
Selects strips all intersecting this rectangle.
Box Select (Include Handles) Ctrl-B
Works the same as Box Select but it selects only the strip’s handles,
if just one handle is selected moving the strip after selecting will change the strip’s length.
If both handles are selected the strip will move and behave the exact same as Box Select.
Side of Frame
Select strips laying left or right to the current frame.
Select strips intersecting with the current frame.
Operators to select strip handles.
These operators are useful to change the timing of a cut by moving the handles after selecting them.
Both, Left, Right
Select the left, right, or both handles of selected strips.
Select the handle of the neighboring strip to the left, right, or on both sides of the selected strips.
Select strips in the same channel laying left or right to active strip.
All Ctrl-L / Less Ctrl-NumpadMinus / More Ctrl-NumpadPlus
Selects strips, that are placed next to each other without any gaps.
Selects strips according to their relation with other strips.
Selects any strips of the same type within a category for example,
if you have a Cross strip selected this will select all other effect strips.
Selects any strips of the same type, e.g. Effect, Image, Movie, etc.
Selects all effect strips.
Selects strips that share the same data, for example, two image strips sharing the same image file.
Selects the strip that shares an effect strip.
Selects the effect strips, if any, linked to the currently selected strip.
Selects any strips that occur on the same frame as the current.