Nanoscale modulation of flat bands via controllable charge density wave defects in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>4</mml:mn> <mml:mrow> <mml:mi>H</mml:mi> <mml:mi>b</mml:mi> <mml:mtext>−</mml:mtext> <mml:

Electron correlation is a main driver of exotic quantum phases and their interplay. The $4Hb\text{\ensuremath{-}}\text{Ta}{\mathrm{S}}_{2}$ system, possessing an intrinsic heterostructure of $1T$- and $1H\text{\ensuremath{-}}\text{Ta}{\mathrm{S}}_{2}$ monolayers, offers a unique opportunity to control electron correlation by distorting the atomic lattice or tuning interlayer coupling. Here, we investigated intrinsically deformed charge-density waves (CDWs) in the $1T$ layer of $4Hb\text{\ensuremath{-}}\text{Ta}{\mathrm{S}}_{2}$ to elucidate and control their effects on flat bands using scanning tunneling microscopy and spectroscopy (STM/S) combined with first-principles calculations. We identified two types of CDW defects: Type 1 has structural distortion and locally suppressed flat bands, while Type 2 features an increased flat band filling factor of intact CDW structure. Density functional theory calculations indicate that a sulfur vacancy in the $1T$ layer distorts the CDW structure and gives rise to a Type 1, whereas a sulfur vacancy in the $1H$ layer reduces the interlayer charge transfer and leads to a Type 2. Furthermore, we demonstrated creating and erasing individual CDW defects via STM manipulation. Our findings provide a pathway to not only tune flat bands but also selectively manipulate the interaction between CDW, the atomic lattice, and interlayer coupling in strongly correlated systems with atomic precision.