Drawing-Object Caps

line.new(bar_index - 20, high[20], bar_index, high, color=color.lime, extend=extend.right)

Over 500 bars this hits the cap and the oldest line keeps disappearing.

indicator("…", max_lines_count=50)

Keeping only the last 50 lines makes the pruning intentional and keeps the snapshot small (every live drawing is sent to every viewer).

Hold a reference and delete the previous one when a new one is created:

var line current = na
if ta.change(ta.highest(high, 20)) != 0
    line.delete(current)
    current := line.new(bar_index - 20, high[20], bar_index, high,
                        color=color.lime, extend=extend.right)

var array<line> ring = array.new<line>()

if newPivot
    if ring.size() >= 20
        line.delete(ring.shift())
    ring.push(line.new(bar_index, high, bar_index + 10, high, color=color.lime))

The ring buffer gives you deterministic control over which drawings survive.

• Lines and boxes
• Declaration statements